Temperature-sensing patch

ABSTRACT

This temperature-sensing patch comprises a flexible backing web having a pressure-sensitive adhesive coated on one side and a plurality of discrete temperature-sensitive, color-responsive indicators adhered on the other side thereof. Each of the indicators comprises a layer of encapsulated liquid crystals which change in color responsive to temperature changes within a predetermined temperature range.

United States Patent Flam [451 May 9,1972

[54] TEMPERATURE-SENSING PATCH [72] Inventor: Eric Flam, East Brunswick,NJ.

[73] Assignee: Johnson & Johnson [22] Filed: Feb. 5, 1970 [21] Appl.No.: 8,902

Geldmacher ..73/356 X Gander et al. l28/l56 ABSTRACT [52] "128/2 H,73/356 This temperature-sensing patch comprises a flexible backing [51]hit. Cl. ..A61b 10/00 web having a pressure sensitive adhesive coated onone side Fleld 0 Search 2 H; and a plurality of discrete temperaturesensitive color 56 R f ed responsive indicators adhered on the otherside thereof. Each 1 e erences of the indicators comprises a layer ofencapsulated liquid UNITED STATES PATENTS crystals which change in colorresponsive to temperature 2 385 0/1961 w h t l 73/356 changes withinapredetermmed temperature range. 3,00 a e a 3,533,399 10/1970 Goldberget al ..l28/2 R 16 Claims, 5 Drawing Figures TEMPERATURE-SENSING PATCHBACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to a field of temperature-indicating devices. Moreparticularly, it relates to an inexpensive patch which is adhered to asurface to visually indicate the temperature thereof by a color responsewhich is related to a predetermined color-temperature relationship.

While the present invention will be described in connection withparticular embodiments designed primarily for sensing and visuallymonitoring thermal patterns in human skin, it should be understood thatthe use of the invention is not necessarily limited thereto. It can beemployed for sensing and monitoring the surface temperature of a varietyof other animate and inanimate objects to which it can be adhered, e.g.,testing the heat distribution of electronic circuits and devices anddetecting the flow paths of internally generated heat in variousmechanical and other devices.

2. Description of the Prior Art It is now well recognized that skintemperature measurements may be a valuable tool in the field of medicaldiagnostic and monitoring procedures. For example, recent studies havesuggested that localized skin temperature variations may be correlatablewith subsurface events such as inflammations, cardiovasculardifficulties and tumors. Various prior art devices are available formeasuring skin temperature but they suffer from one or more shortcomingswhich have inhibited their extensive use.

For example, metallic skin thermometers require a long time to read and,because they are not always conformable to skin surfaces having variedand changeable conformability requirements, the readings are not alwaysas accurate as desired. Temperature-sensing electrical probes areexpensive, involve complex equipment, are inconvenient to set up, andotherwise are not practical for many purposes. Infrared scanners arealso very expensive, require complex equipment which is not readilyavailable at desired locations, and otherwise suffer from variousdifficulties known to those skilled in the art.

Prior-art techniques for utilizing liquid crystals for such temperaturemeasurements have similarly suffered from shortcomings. Types of backingmaterials have been restricted; temperature ranges have been limited;application techniques have been inconvenient; stability problems havebeen present; accuracy has suffered; poor conformability, delaminationand contact problems have been encountered; and poor flexure resistancehas been experienced.

It is therefore a general object of the present invention to provide atemperaturesensing patch which copes with the difficulties encounteredwith the prior art devices.

It is a more specific object of the present invention to provide atemperature-sensing patch which is inexpensive, convenient to use,provides a continuous reading over a substantial temperature range andis characterized by a sensitive, accurate and very rapid visualtemperature response.

It is still another object of the present invention to provide alow-cost, temperature-sensing patch which can detect a substantial rangeof temperatures at substantially the same location.

It is still another object of the present invention to provide a stable,accurate, sensitive and low-cost visual temperaturesensing patch whichcan be applied at multiple locations, is highly conformable to theunderlying skin, and is not adversely affected by repeated flexure.

It is still another object of the present invention to provide atemperature-sensing patch of high conformability and versatility whichextends the practical range of prior-art liquid crystal temperaturesensing devices.

These and other objects of the present invention will become apparent asa detailed description thereof proceeds.

SUMMARY OF THE INVENTION These objects are achieved in a particularembodiment of the present invention by a temperature-sensing patch whichcomprises a flexible backing web having a pressure-sensitive adhesivecoated on one side thereof for holding the flexible backing web in tightdirect contact with the underlying skin. On the other or exposed side ofthe web is disposed a plurality of discrete temperature-sensitive,color-responsive indicators, each of which comprises a layer ofencapsulated liquid crystals (sometimes abbreviated ELC's). Each of theindicators displays a color change spectrum corresponding to temperaturechanges within a different predetermined temperature range. Adjacentindicators on the patch preferably cover overlapping temperature rangeswhereby, in effect, a patch is produced displaying a continuous colorchange over an extended temperature range.

In a preferred embodiment the backing web is circular and the indicatorson the surface thereof are disposed in spaced pie-shaped sectors aboutthe center. Other configurations may also be employed, e.g., square,rectilinear and the like. The web is substantially black in color andthe pie-shaped sectors are separated or spaced by a border ofcontrasting color, preferably white.

In still other embodiments, the temperature-sensing patch as a whole oreach of the indicators individually is covered with an overlying,substantially-transparent flexible covering such as a transparentplastic film or clear lacquer coating. Additionally or alternatively, aplasticizer or humectant may be added to the ELCs and/or a primercoating may be added to the backing to enhance fracture and delaminationresistance. These and other embodiments are discussed in detailhereinafter.

THE FLEXIBLE BACKING WEB The flexible backing web may comprise anysuitable thin film which can be adhered and readily conform to thecontours of the underlying skin and to which the ELCs can be adheredwithout proneness to separation or delamination under normal flexureconditions. Because the liquid crystals are encapsulated, stable patchescan be prepared using both polar and non-polar polymers. Suitable filmsinclude polyvinyl chloride films, polyolefin films such as polyethyleneor polypropylene, polyethylene terephthalate, polyvinylidenechloride-polyvinyl chloride copolymer, polyurethane films, regeneratedcellulosic films, paper, natural and synthetic fabrics and the like,preferably polyvinyl chloride.

Depending upon the particular film selected, the thickness thereof istypically in the range of0.5 mils to l5 mils, e.g., l to 10 mils,preferably 2 to 3 mils in the case of polyvinyl chloride film. Thinfilms are preferred to decrease cost, reduce the mass, enhanceflexibility and conformability and to bring the color-responsiveindicator as close as possible to the underlying skin surface.Manifestly, the thinner the film, the less the mass and the thermalinsulation between the indicator and skin and the more rapid thetemperature response. The film, however, should not be so thin as tolack the requisite strength or to encounter the curl under edge problemassociated with very thin webs having adhesive coatings.

The color of the film is preferably black although other colors may alsobe employed, e. g., red, yellow, green and blue. The latter, however,have generally been found to be inferior to black for detecting andviewing ELC color changes.

THE PRESSURE-SENSITIVE ADHESIVE The adhesive which is applied to theflexible backing web can be any conventional pressure-sensitive adhesivewhich will adhere the web throughout its area to the surface beingmonitored, whereby good thermal contact is achieved. For measuring skintemperatures, any mass that has acceptable clinical properties issuitable for providing adhesion of the patches to the skin. Theseinclude the rubber base and the acrylate pressure-sensitive adhesives.

One operable form of pressure-sensitive adhesive is a pure rubberycopolymer of isooctyl acrylate and acrylic acid in a 94:6 ratio, asdescribed in Ulrich U.S. Pat. No. 2,884,126 (Re. 24,906). Other examplesof suitable adhesives are set forth in U.S. Pat. Nos. 2,877,141,2,909,278, 3,307,544 and 3,325,459.

The amount of adhesive depends upon the particular adhesive, the natureof the surface to which it is applied, the end use of the patch, and thelike. Thin coatings are preferred to decrease the mass and enhance heattransfer and rapidity of response. In the embodiment for sensing skintemperatures, the thickness of adhesive may typically be in the range of0.3 to 3 mils, preferably 0.5 to 1 mil.

The adhesive may be applied to the backing web by conven tionaltechniques, including, for example, transfer techniques, the use of akissing roll, and the like. If spread from a solvent, the coating isdried and, if necessary, cured.

Depending upon the nature of the adhesive and the backing web, a primermay be applied to the web to anchor the adhesive mass. In the case of anacrylate adhesive and a polyvinyl chloride backing web, for example, apolymeric primer of the type disclosed in U.S. Pat. No. 2,647,843 may beemployed, i.e., a butadiene-acrylonitrile copolymer and SBR (styrenebutadiene rubber). In the case of an acrylate adhesive and apolyurethane backing web, no primer may be required.

To cover the pressure-sensitive adhesive prior to use, a peelable facingmaterial may be employed, e.g., cellulose acetate, regenerated cellulose(cellophane), resin coated papers and the like. These and others aredescribed, for example, in U.S. Pat. No. 2,703,083.

Various release agents which improve the releasability characteristicsof the facing may be added to the facing, e.g., stearato chromicchloride, sold by Du Pont Company under the trademark Quilon."

THE COLOR-RESPONSIVE INDICATORS The temperature-sensitive,color-responsive indicators employed in the practice of the inventioncomprise cholesteric" liquid crystals, which contain cholesteric esterssuch as cholesteryl pelargonate (nonanate), cholesteryl chloride, oleylcholesteryl carbonate, and the like, and have the property of changingcolor with change of temperature. They can be tailored, for example, tochange color at different temperatures in the temperature range of 20 Cto 250 C. Background information is set forth in Scientific American, 21l:76 August, I964, at pages 77-85.

The liquid crystals employed in the present invention are contained intiny capsules, e.g., to 50 microns, typically to 30 microns.Encapsulation provides a longer shelf life, greater reproducibility ofresults, overall improved stability and a greater ease in handling. Theyrespond to temperature changes within about 0.1 to 0.5 seconds, e.g.,0.2 seconds.

ELCs covering a series of overlapping temperature ranges arecommercially available. See, for example, Product Information Bulletin681 of The National Cash Register Company, Dayton, Ohio, wherein 16available and overlapping temperature ranges are listed and designatedas follows:

ELCs are supplied as a water-based slurry, which can be applied to thebacking web by conventional techniques, e.g., swabbing, disposition froma disposable pipette, brushing or painting, machine coating using an airknife to control film thickness, spraying, air brushing, using a Gardnerbar, Mier rods and Gravure tool, and the like. To assure that the ELCsadhere tightly and securely to the backing web and resist delaminationupon flexing, a primer may be applied and dried before application ofthe ELCs.

The need for and the type of primer depend in part upon the type ofbacking web. For example, when employing polyvinyl chloride film as thebacking web, the primer may comprise a colloidal aqueous suspension ofindividual spherical particles of butadiene-acrylonitrile Americanrubber. A suitable form of this suspension is sold as Hycar 157i Latexby B. F. Goodrich Chemical Company. Other suitable primers are theaforementioned primers of U.S. Pat. No. 2,647,843.

The primer may be applied in amounts of, for example, 0.2- to-] ounceper square yard, typically about 0.7 ounce per square yard in the caseof Hycar 1571. Conventional application techniques may be employed,e.g., swabbing, reverse roll techniques, air-knife coating, Meir rod orroll techniques, and the like.

To eliminate any tendency of the ELC film to separate, delaminate orcrack, a plasticizer or humectant may be included in the slurry of ELCsat the time it is applied to the backing web. Conventional plasticizersknown to those skilled in the art may be employed, e.g., glycerol,propylene glycol and the like. For example, satisfactory results wereobtained when 0.08 ml of glycerol was admixed to a slurry of 6 ml ofELCs and 3 ml of distilled water. In specific embodiments,glycerol-plasticized ELCs were successfully attached to black paper(Dexter X-l574-100, produced by C. H. Dexter & Sons) both with Hycar1571 Latex as a primer and also without any primer.

Alternatively, the ELC film may be covered with an overlying,substantially-transparent flexible covering such as a transparent filmor clear lacquer coating. The transparent flexible covering may take theform of, for example, a thin polyethylene or cellophane covering, whichmay be adhered by conventional adhesives or other securing techniques,such as thermal welding. The clear lacquer coating may comprise aconventional thin spray coating of a clear lacquer which is resistant tosurface grazing when subject to flexure, e.g., Grant's Clear Lacquer No.44594, as sold by W. T. Grant & Co. The coverings protect the ELC layerfrom dust deposition and scratches, act as a mechanical seal for theprimer and ELC layers, lock them to the flexible backing web and act asa barrier to excessive moisture loss from the ELC layer, thusmaintaining the latters resistance to fracture or delamination.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be moreclearly understood from the following detailed description of specificembodiments, read in conjunction with the accompanying drawings,wherein:

FIG. I shows a typical temperature-color relationship for one rangeofcommercially-available ELC's;

FIG. 2 shows one embodiment ofa patch of the present invention whereinthe patch is circular and three discrete indicators covering overlappingtemperature ranges are disposed about the center in pie-shaped sectors;

FIG. 3 is a greatly-magnified fragmentary section taken on the line 33of FIG. 2;

FIG. 4 is a fragmentary view of a typical temperature-color comparisonchart which may be used to interpret the color presentation observedwhen employing temperature-sensing patches of the type shown in FIG. 2;and

FIG. 5 shows another embodiment wherein the ELCs are disposed in 16pie-shaped sectors on the patch and formulated so as to give a directtemperature indication as each segment changes color with change intemperature.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. 1, thetemperature of the ELC layer in degrees Centigrade is plotted againstthe theoretical wave length of reflected light and the resulting colorthereof as viewed by an observer. This relationship obtains forcommercially-available ELCs designated as R-33, as produced by TheNational Cash Register Company, Dayton, Ohio. The plotted range is 33 Cto 37 C. Below 33 C the observed color is black when viewed in whitelight. As the temperature is raised through the 33 C to 37 C range, theobserved color theoretically changes progressively from black to red toyellow to green to blue to black again.

The changes are described as theoretical because it is difficult to seethe reds and yellows. Black is easily seen, green is quite distinct, andblue is clearly visible. Intermediate colors between blue and green arealso quite discernible. Thus, although a single ELC indicatortheoretically provides a temperature sensing range of 4 C (over 7 F) asshown above and in the chart on page 8 of this specification, itseffective range is usually no more than 2 C (3.6 F). For most purposes,a more extended range is necessary, e.g., at least about 6 C 1 1 F) forskin temperature sensing applications. The limited range is adequatelycoped with by the present invention as will become apparent from thedetailed description and data hereinafter presented.

Because of the aforementioned difficulty in detecting certain colors andsince the wave length and color of reflected light is in part a functionof the wave length and color of the incident light, tests were conductedwherein the color of the incident light was varied from the conventionalwhite" light usually employed, the white" light being that produced froman unfiltered incandescent light source. The colors were achieved bysuccessively placing blue, green, yellow and red cellophane sheets infront of the white" incandescent light source. The effects of the colorfilters on the observed colors of the reflected light from the ELCpatches, as compared to the observed colors using white" light, are asfollows:

Observations of EL C Colors yellow cannot be seen The data indicate thatblue, green or yellow light may offer viewing advantages overconventional white light and that red is much poorer.

As those skilled in the art will recognize, the use of differentcolored" light sources extends the utility of the present invention. Forexample, as shown in FIG. 1, the ability to detect yellow by using ayellow incident light provides a very sensitive temperature indicationinasmuch as the yellow band covers a very narrow temperature band. Suchrelationship could be helpful in constructing the embodiment of thepresent invention illustrated in FIG. 5, discussed hereinafter.

Referring to FIGS. 2 and 3, circular patch 10, which typically might be$4 to 1 inch in diameter, size being a matter of cost, convenience andend use, comprises flexible backing web 12, e.g., a 2 to 3 mil film ofblack polyvinyl chloride, having pressure-sensitive adhesive 14 on oneside thereof and three pie-shaped temperature-sensitive,color-responsive indicators l6, l8 and on the opposed side thereof. Inthis embodiment the indicators are securely fastened to web 12 by meansof primer layer 22, e.g., the aforementioned I-lycar 1571. Optionally,indicators l6, l8 and 20 are protected by an overlying covering 24,e.g., a thin film of transparent polyethylene or the like or a spraycoating of clear lacquer.

Indicator 16 may comprise a layer of the aforementioned ELC's designatedR-29, covering a theoretical temperature range of 29 C to 33 C.Similarly, indicator 18 may contain ELCs designated R-31, covering atheoretical temperature range of 31 C to 35 C. Likewise, indicator 20may comprise ELCs designated R-33, covering a theoretical temperaturerange of 33 C to 37 C. The ELCs designated as R-29, R-31 and R-33comprise blends of the cholesteric esters cholesteryl pelargonate(nonanate), cholesteryl chloride, and oleyl cholesteryl carbonate.

The three indicators are separated or spaced by a border 26 ofcontrasting color, preferably white. The border 26 may be printed orpainted onto the backing or may comprise paper, thin plastic includingpolyvinyl chloride, or the like, which is adhered by conventionaltechniques to the underlying polyvinyl chloride film 12. So thatindicators 16, 18 and 20 are readily distinguishable, any form ofconvenient identification means may be employed such as, for example,the one-dot, two-dot, and three-dot system illustrated. The dots may besuperposed over the indicators, as shown, placed on an adjacent annularborder, or otherwise conveniently located.

While not shown in FIG. 3, pressure-sensitive adhesive 14 may be adheredto web 12 by means of a primer coating. in still other embodiments,primer coating 22 or covering 24 may be omitted. In the latter case, ELClayer 20 should contain a plasticizer or humectant, e.g., glycerol, toavoid drying out and associated delamination problems.

To assist in interpreting the color presentation shown on patch 10, acolor comparison chart 28 of FIG. 4 may be employed. Chart 28 shows whatan observer would expect to see at each of the indicated temperatureswhen viewing the patch at each of the indicated temperatures. Theidentifying dots are located outside the periphery of the patch forconvenient reference. Such a chart may be prepared, for example, bysubjecting a typical patch to a carefully controlled temperature bath.The observed color presentation at a series of temperature increments isthen reproduced in chart form as shown at 29a, 29b, etc. in FIG. 4.

The use of pie-shaped sectors for the patch of the present invention hasthe advantage that each of the discrete indicators has a portionadjacent the center. Thus, in effect, the entire range of indicators canread the temperature adjacent the center, that is, substantially at onepoint.

Another embodiment of the present invention is shown in FIG. 5 whereinl6 discrete indicators 40 are disposed in pieshaped sectors about center42 of patch 44. Each of the indicators 40 is separated from the adjacentindicator by radial spacers 46, which are preferably white in color.Annular border 48 is provided so that temperature indicia may be printedthereon. In the exemplar of Exhibit 5 these indicia are set forth in 1Fahrenheit increments.

Indicators 40 of patch 44 are formulated whereby the brightest or mostreadily observable color dominates at the particular temperature shownat that segment. Thus, such color would appear in clockwise successionas the temperature is raised. For comparison, center portion 42 couldshow the color which is encountered when the indicated temperature issuccessively achieved in each successive pie-shaped segment.

As aforementioned, this embodiment might also be used with coloredincident light to take advantage of the increased sensitivity resultingtherefrom. Thus, a yellow light source might be used and the ELCS ofeach segment might be formulated to reflect yellow light at each of theindicated temperatures. These and other embodiments are apparent tothose skilled in the art in the light of the present disclosure.

EXAMPLES Example 1 Trisector patches similar to FIG. 2, but having anannular border similar to that of FIG. 5, are prepared by the followingsteps:

1. A black polyvinyl chloride tape having a pressure-sensitive adhesivesecured to one side thereof is provided; 2. The adhesive-free side iscleaned with ethanol and air dried; 3. A 1% inch wide masking tapehaving 7/8 inch diameter holes with the desired trisector grid spaced at1% inch centers is applied to the adhesive-free surface;

4. A latex-base primer is applied to each of the three exposed sectorswith a cotton swab and allowed to air dry at room temperature for 30minutes, followed by a -minute bake at 160 F;

. A diluted suspension of ELCs (two volume parts of ELC to one volumepart of water) is then applied with a swab to each of the sectors with a2-hour air drying period between successive applications to minimizecross mixing, the ELC's in the three sectors being the aforementionedR-29, R-3l and R-33, respectively;

6. Two coats of clear lacquer are sprayed over the ELC- coated sectorsand masked areas with -minute intervals between each spraying andallowed to air dry at room temperature; and

7. 1% inch diameter patches with the "/s-inch ElC-coated trisector arecut out of the tape to provide skin patches, having the characteristicshereinabove described.

A series of tests were carried out employing patches prepared as abovedescribed. These patches were placed on a surface that was heated, andcolor observations using white" incident light were made in 05 Cincrements from 29 C through 38 C. Data obtained for one of the patchesare as follows:

LII

Observed Color of Each Patch Sector Substantially the same data wereobtained with three similar notches. Such data can be employed, forexample, in the preparation of color comparison chart 28 of FIG. 4.

Example 2 Trisector patches similar to FIG. 2 are prepared substantiallyas described in connection with Example 1 except that the clear lacquerspray coatings are eliminated. This minimizes the possibility of surfacecrazing when the patches are subjected to repeated flexure, but couldunduly accelerate drying out of the ELC coating. To prevent undue dryingand possible delamination of the ELC coating, a humectant or plasticizerin the form of glycerol is added to the slurry of ELC prior toapplication to the primer-coated polyvinyl chloride backing. After 250complete 360 flexes, this construction shows no tendency to delaminateor crack. Temperature'color response is substantially the same as inExample 1.

Further tests also show that the process of Example 1 can be simplifiedsomewhat. The 5-minute baking period at 160 F of step 4 can beeliminated without affecting the adhesion of the primer to the backingor the ELC to the primer. The ELC slurries can also be added to each ofthe sectors using a disposal pipette rather than a cotton swab. A moreuniform suspension results.

From the above description it is apparent that the objects of thepresent invention have been achieved. The temperaturesenslng patchconforms to the contours of the skin and provides good thermal contact.It covers a wide range of temperatures; and because of its overall lowthermal mass, it gives a very rapid response. It is very stable insensing temperature and is otherwise mechanically sound. While onlycertain embodiments have been illustrated, many alternativemodifications will be apparent from the above description to thoseskilled in the art. These and other alternatives are considered withinthe spirit and scope of the present invention, and coverage thereof isintended by this application.

Having described the invention, what is claimed is:

1. In a temperature-sensing device for indicating surface temperatureswith temperature-sensitive, color-responsive liquid crystals, theimprovement which comprises a patch comprising:

a. a flexible backing web;

b. a pressure-sensitive adhesive coated on one side thereof;

and

c. a plurality of discrete temperature-sensitive, colorresponsiveindicators adhered on the other side thereof, each of said indicatorscomprising a layer of encapsulated liquid crystals, the color spectrumof each indicator being responsive to the temperature of the indicatorwithin a predetermined, continuous temperature range.

2. The temperature-sensing patch of claim 1 wherein the predeterminedtemperature range of each indicator differs.

3. The temperature-sensing patch of claim 2 wherein the predeterminedtemperature range of adjacent indicators overlap.

4. The temperature-sensing patch of claim 1 wherein the adjacentindicators are separated by a border of contrasting color.

5. The temperature-sensing indicator of claim 1 wherein said backing webis circular and said indicators are disposed in spaced pie-shapedsectors about the center thereof.

6. The temperature-sensing patch of claim 5 wherein said web issubstantially black in color and the spaces between adjacent indicatorsare substantially white in color.

7. The temperature-sensing patch of claim 1 including an overlyingsubstantially-transparent flexible covering for said indicators.

8. The temperature-sensing patch of claim 7 wherein said coveringcomprises a transparent plastic film adhered thereto.

9. The temperature-sensing patch of claim 7 wherein said coveringcomprises a clear lacquer coating.

10. The temperature-sensing patch of claim 1 wherein the encapsulatedliquid crystals of each indicator contain a plasticizer to enhanceconformability of each indicator to said flexible backing web.

11. The temperature-sensing patch of claim 10 wherein said plasticizercomprises glycerol.

12. The temperature-sensing patch of claim 1 wherein said flexiblebacking web comprises a black polyvinyl chloride film.

13. The temperature-sensing patch of claim 1 wherein saidpressure-sensitive adhesive is an acrylate-type adhesive.

14. The temperature-sensing patch of claim 1 including a primer coatingon said other side thereof to increase the adhesion of said indicatorsto said web.

15. The temperature-sensing patch of claim 14 wherein the primer coatingcomprises a dried latex colloidal suspension.

16. The temperature-sensing patch of claim 1 including a peelable facingmaterial covering the exposed surfaces of said pressure-sensitiveadhesive.

2. The temperature-sensing patch of claim 1 wherein the predeterminedtemperature range of each indicator differs.
 3. The temPerature-sensingpatch of claim 2 wherein the predetermined temperature range of adjacentindicators overlap.
 4. The temperature-sensing patch of claim 1 whereinthe adjacent indicators are separated by a border of contrasting color.5. The temperature-sensing indicator of claim 1 wherein said backing webis circular and said indicators are disposed in spaced pie-shapedsectors about the center thereof.
 6. The temperature-sensing patch ofclaim 5 wherein said web is substantially black in color and the spacesbetween adjacent indicators are substantially white in color.
 7. Thetemperature-sensing patch of claim 1 including an overlyingsubstantially-transparent flexible covering for said indicators.
 8. Thetemperature-sensing patch of claim 7 wherein said covering comprises atransparent plastic film adhered thereto.
 9. The temperature-sensingpatch of claim 7 wherein said covering comprises a clear lacquercoating.
 10. The temperature-sensing patch of claim 1 wherein theencapsulated liquid crystals of each indicator contain a plasticizer toenhance conformability of each indicator to said flexible backing web.11. The temperature-sensing patch of claim 10 wherein said plasticizercomprises glycerol.
 12. The temperature-sensing patch of claim 1 whereinsaid flexible backing web comprises a black polyvinyl chloride film. 13.The temperature-sensing patch of claim 1 wherein said pressure-sensitiveadhesive is an acrylate-type adhesive.
 14. The temperature-sensing patchof claim 1 including a primer coating on said other side thereof toincrease the adhesion of said indicators to said web.
 15. Thetemperature-sensing patch of claim 14 wherein the primer coatingcomprises a dried latex colloidal suspension.
 16. Thetemperature-sensing patch of claim 1 including a peelable facingmaterial covering the exposed surfaces of said pressure-sensitiveadhesive.